Dental implant and method of mounting the same

ABSTRACT

An implant designed to be mounted specifically in the ramus or retromolar portion of the mandible or jawbone, having an elongated main body carry a post extending up from the forward end of the main body and passing up through the epithelium; the main body of the implant being inserted into a partial incision made in the bone in a direction extending longitudinally and rearwardly, and driven in through and rearwardly beyond the incision and in beneath the top surface of the ramus; the main body of the implant extending rearwardly spaced a safe distance above the alvealor nerve and positioned between the signal lingual and buccal cortical plates of the ramus.

United States Patent [72] Inventor Harold D. Roberts 2717 N. E. KnottSt., Portland, Oreg. 97212 [21] Appl. No. 843,579 [22] Filed July22,1969 [45] Patented May 11, 1971 [54] DENTAL IMPLANT AND METHOD OFMOUNTING THE SAME 4 Claims, 6 Drawing Figs.

[52] 11.5. CI 32/10 [51] Int. Cl A6lc 13/00 [50] Field of Search 32/10(A) [56] References Cited UNITED STATES PATENTS 2,721,387 10/1955Ashuckian 32/10 3,465,441 9/1969 Linkow 32/10 OTHER REFERENCES ImplantResearch Corporation Publication, 2 pages, Copyright 1968 PrimaryExaminerRobert Peshock Attorney-L. R. Geisler ABSTRACT: An implantdesigned to be mounted specifically in the ramus or retromolar portionof the mandible or jaw bone, having an elongated main body carry a postextending up from the forward end of the main body and passing upthrough the epithelium; the main Body of the implant being in- PatentedMay 11, 1911 I 3,577,853

HAROLD DL ROBERTS -WATTY.

INVENTOR.

DENTAL IMPLANT AND METHOD OF MOUNTING THE SAME BACKGROUND OF THEINVENTION Various types of implants have been developed during recentyears for anchoring artificial dentures to the bone structure. Some ofthese comprise subperiosteal skeleton saddles secured to or on themandible. One problem with these is the tendency of resorption to takeplace under the saddle or implant, causing a slight undermining to occurbeneath the same which must be accommodated.

Other types of implants comprise pins or composite posts driven orthreaded into a blind hole cut into the bone. A number of designs forsingle and composite posts of such types have been developed, a recentexample being the implant device described in US. Pat. No. 3,435,526,issued Apr. 1, 1969 to Brancato. Often such implants, however, cannot beused in the bicuspid and molar portion of the mandible. This isparticularly true if atrophy of the bone has set in, and in this portionof the mandible atrophy is not uncommon in older persons. In cases ofthis nature reliance on intraosseous implants in the bicuspid and molarportion of the mandible must be wholly or partly avoided by theemployment of a bridge with an end secured on the implant placed in theramus portion of the mandible where the dense and better conditionedbone structure offers a better implant anchorage. However, the depth towhich an implant post can extend, even in the ramus, is limited by thelocation of the inferior alvealor nerve since the bottom of the implantmust not extend into too close proximity to the alvealor nerve andartery. Consequently a single pin, or even the composite pin describedin U.S. Pat. No. 3,435,526, mentioned above, implanted to thenecessarily limited depth in the ramus, cannot provide a bridge endsupport entirely capable of satisfactorily withstanding the movingstresses imposed in mastication.

The object of the present invention is to provide an improvedpermanently and firmly set implant, specifically developed to provideanchorage in the ramus, which can be driven rearwardly into the ramusand which will have a much greater area of contact within the bonestructure and will, consequently, be more securely held by the bone, andalso with which any possibility of approaching too close to the alvealornerve area will be avoided.

OUTLINE OF THE INVENTION The implant of the present invention comprisesan elongated main body portion, specially adapted for being drivenrearwardly into and imbedded in the ramus bone, with the main bodyportion carrying a post extending from the main body portion and throughthe epithelium to serve as the mounting for an artificial denture orportion of a dental bridge. The imbedded main body portion has athickness of only approximately 2.0 mm. and a width or depth preferablynot exceeding 5.0 mm. It is formed with a plurality of perforationsenabling the bone to grow into the perforations in the mannercharacteristic of the healing or growth tendency of the inferior andsuperior maxilla in closing bone openings.

For an implant in the ramus an implant having a main body portionpreferably approximately 31.5 mm. in length is used, the implant beingset approximately along the longitudinal medial line and in between thelingual and buccal plates of the ramus. For such an implant an incisionis cut into the bone not over 2.0 mm. in width, 6.0 mm. in depth, andpreferably not over 18.0 mm. in length. The implant is then tappedrearwardly into the bone for a distance corresponding to the remainderof the length of the main body portion beyond the end of the incision.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side elevation of an implant embodying the present inventionand thus designed specifically for being implanted in the ramus;

FIGS. 2 and 3 are corresponding side elevations of similar implants withthe post extending up at different angularities with respect to the mainbody portion;

FIG. 4 is a cross section on line 4-4 of FIG. 1 drawn to an enlargedscale;

FIG. 5 is a diagrammatic representation illustrating an implant inposition in the left ramus, the ramus portion of the mandible beingindicated in broken lines; and

FIG. 6 is a perspective view of a mandible bone illustrating a pair oframus implants formed and mounted in accordance with the presentinvention and positioned in the two ramus end portions of the mandiblebone respectively.

Referring first to FIG. I, the implant of the present invention, adaptedexclusively for mounting in the ramus of the mandible, consists of anelongated body portion 10 and an integral post 11 extending up from oneend of the body portion.

Since the end on which the post 11 is carried will be at the rear of theimplant, as the implant is driven rearwardly into place in the ramus inthe manner later explained, the post 11, for the purpose of thisdescription, will be mentioned as located at the forward end of the bodyportion 10, when the body portion is anchored in place.

The body portion 10 is designed to be mounted entirely within the bone,and thus within one one of the ramus end portions of the mandible bone.When the body portion 10 has been properly set in place in the bone thepost 11 will extend up through the epithelium or mucous membrane andskin covering the bone, so as to provide a desired denture support.

In order to cause the implant to be held more securely in place in thebone, the body portion 10 is formed with a plurality of holes 18 topermit the bone growth to enter these holes and thus cause the bodyportion to become more rigidly anchored in the bone. As is well known, acharacteristic of jawbones is to tend to grow into and to close upopenings within the bones. Also, the side faces 16 and 17 of the bodyportion 10 of the implant, as shown best in FIG 4, are preferablyconcave with respect to the substantially vertical plane along which theimplant is set so as to cause the bone growth to fill in the voidssurrounding the holes 18 and add further to the hold of the bone of thebody portion 10. The bottom edge 13 of the body portion 10 is upwardlycurved as shown in FIG. I.

The inner end of the body portion (with respect to the direction withwhich the body portion is inserted into the bone) terminates in anarrowed tip 14 to facilitate the thrusting or tapping of the bodyportion into place in the bone, preferably in accordance with the methodand procedure now to be explained.

Assuming that the implant is to be set in the ramus R on the left sideof the mandible M (as illustrated in FIG. 5), the dentist, with the aidof X-rays, determines the most advantageous and serviceable place forthe implant, taking into consideration the condition of the bone, theangle of the anterior border of the mandible ramus, and the amount ofthe bone above the alvealor nerve. In FIG. 5 the alvealor nerve isdiagrammatically indicated by the line N. Also, the dentist determineswhich of the available implants (thus, for example, the implant of FIG.1 or FIG. 2 or FIG. 3) will be most suitable to use. It will be notedthat the only difference in the implants of FIGS. 1, 2 and 3 is the sizeof the angle between the post 11 and the top edge 12 of the body portion10 (thus the angle indicated at X, Y and Z in FIGS. 1, 2 and 3respectively). Since the post 11 should extend up substantiallyvertically when the implant is in place, the dentist decides the amountof angularity of the body portion 10 with respect to the post whichwould be best under the particular circumstances present. It will beapparent that the angle X, -Y or Z would never exceed and generally willbe considerably less.

The area in which the ramus implant in question is to be located willgenerally be from 25 to 28 mm. distal to the mental foramen in themandible. When severe resorption of the bone has taken place, forexample in elderly patients, the dentist may position the implantfurther back in the ramus of the mandible in order to have it anchoredin better and more serviceable bone.

Having decided on the particular implant and the best location for itsmounting, the dentist makes an incision through the oral tissue anduncovers the top of the bone where the bone incision is to be located.An incision is then made in the bone, the width of the bone incisionbeing no greater than 2 mm., or the thickness of the body portion of theimplant, the depth of the bone incision preferably being no greater than6 mm., and the length longitudinally of the bone incision preferablybeing not greater than 18 mm. if the length of the body portion 10 ofthe implant is approximately 31.5 mm. which is the preferred length forsuch ramus implant. With the body portion 10 of the implant insertedinto the incision of the bone, the implant is then tapped into the bonebeyond the previously made bone incision for a distance equal to theremaining length of the body portion, The top and bottom edges 12 and 13of the body portion 10 merge into the tip 14 (FIG. 1) at the inner orforward end of the body portion 10, as previously mentioned, tofacilitate the penetration of this forward portion of the body into thebone during the tapping of the implant into place, and the fact that theimplant enters in between the lingual and buccal cortical plates of theramus of the mandible and, consequently, into the somewhat less denseportion of the bone, makes it possible for this tapping of the implantfor the additional distance in the bone to be accomplished withoutdifficulty.

Preferably, the body portion 10 of the implant is fonned with a sharplip l5 (FIG. 1) protruding for a distance of approximately 30 mm. fromthe opposite or forward end. When the body portion has been set entirelyin the bone the implant, through the intermediary of a suitable pullinginstrument, is subjected to tapping in the reverse direction so as tocause this lip 15 to be thrust forwardly under the cortical mesial bonestructure and thus forwardly from the starting point of the boneincision. The entry of this lip under the cortical bone at this pointprevents any possibility of the forward or post section of the implantbeing inadvertently lifted slightly from its bed in the bone duringsubsequent removal of the impression required for the fixed prothesisultimately to be secured to the implant post.

Thus, due to the relatively large area in the bone occupied by the bodyportion 0 for the implant and the formation of the body portion forpromoting firmer anchoring in the bone, the post 11 of the implant ofthe present invention is better suited to supply the necessary rigiddenture support required to withstand permanently the various movingstresses imposed in mastication, and the fact that the implant can be sosatisfactorily placed in the manner and by the method described, withoutany prolonged expenditure of time and efiort on the part of the dentist,and thus without excessive cost as well as without lengthy discomfort tothe patient, provides an improved and very practical solution torecognized specific problems with which the dental profession has had tocontend.

While it is to be understood that minor modifications in the shape ofthe implant and specifically in the body portion of the same, may bemade without departing from the principle of the invention, it isbelieved that the best results are obtained when the implant conformsvery closely to the particular shape and form herein illustrated anddescribed, but it is not intended to limit the invention except as setforth in the claims.

lclaim:

l. The method of mounting an implant in the ramus portion of themandible bone which comprises using an implant having a narrow elongatedbody portion with an upwardly curved bottom edge and a denture-anchoringpost extending up from the forward end of said body portion, cutting alongitudinal slit in the mandible at a predetermined area at the back ofthe mandible, making the width of said slit corresponding to the widthof the body portion of the implant, the depth of the slit notexceeding'approximately 1 mm. the depth of said body portion, but the leth of said slit being less than three-fourths of the length of sai bodyportion, inserting the section of said implant body portion oppositesaid post-carrying end into said slit, and tapping said body portion forthe remainder of its length beyond said slit into the ramus and inbetween the lingual and buccal cortical plates of the ramus, whilemaintaining the curved bottom edge of said body portion a desireddistance above the alvealor nerve, until said body portion is entirelyembedded in the mandible.

2. The method of mounting an implant in the ramus portion of themandible bone which includes using an implant having a narrow, elongatedbody portion with an upwardly curved bottom edge and a sharp lipprotruding for a short distance from the forward end of said bodyportion and a denture-anchoring post extending up from the forward endof the body portion, and which method also consists in cutting alongitudinal slit in the mandible at a predetermined area in the back ofthe mandible, making the width of said slit corresponding to the widthof the body portion of the implant, the depth of the slit not exceedingapproximately i mm. the depth of said body portion, but the length ofsaid slip being less than three-fourths of the length of said bodyportion, inserting the section of said implant body portion opposite thepost-carrying end into said slit, tapping said body portion for theremainder of its length beyond said slit into the ramus and in betweenthe lingual and buccal cortical plates of the ramus while maintainingthe curved bottom edge of said body portion a desired distance above thealvealor nerve, until said body portion is entirely embedded in themandible, and finally tapping said body portion in the reverse directionsufficiently to cause said sharp lip at the forward end of said bodyportion to be thrust forwardly into the cortical mesial bone structurein front of said longitudinal slit, thereby preventing any possibilityof the forward end of said body portion subsequently being slightlylifted from its bed in the mandible.

3. A dental implant designed specifically for insertion rearwardly intothe ramus portion of the jawbone through an incision substantially alongthe longitudinal centerline of the bone .ahead of the ramus portion,said implant having a substantially fiat body portion with a width ofapproximately 2 mm., a depth not exceeding 6 mm. and an overall lengthof at least 30 mm., said body portion having an upwardly curved bottomedge, the top and bottom edges of said body portion converging at therear end of said body portion to form a tip for facilitating the drivingof the rear portion of said body portion rearwardly into the ramus, andan integral post extending up from the forward end of said body portionand adapted, when said body portion is implanted in the bone, to extendup through the epithelium to provide a denture anchorage, the angularitybetween said post and the top edge of said body portion being no greaterthan 4. The ramus implant of claim 3 with said body portion formed witha plurality of holes extending laterally therethrough, and with theaddition of a pointed lip extending from the front end of said bodyportion for a distance of approximately 3 mm., adapted to extendforwardly from the bone incision and under the cortical mesial bonestructure when the implant is tapped forwardly after insertion into theramus.

1. The method of mounting an implant in the ramus portion of themandible bone which comprises using an implant having a narrow elongatedbody portion with an upwardly curved bottom edge and a denture-anchoringpost extending up from the forward end of said body portion, cutting alongitudinal slit in the mandible at a predetermined area at the back ofthe mandible, making the width of said slit corresponding to the widthof the body portion of the implant, the depth of the slit not exceedingapproximately 1 mm. the depth of said body portion, but the length ofsaid slit being less than three-fourths of the length of said bodyportion, inserting the section of said implant body portion oppositesaid post-carrying end into said slit, and tapping said body portion forthe remainder of its length beyond said slit into the ramus and inbetween the lingual and buccal cortical plates of the ramus, whilemaintaining the curved bottom edge of said body portion a desireddistance above the alvealor nerve, until said body portion is entirelyembedded in the mandible.
 2. The method of mounting an implant in theramus portion of the mandible bone which includes using an implanthaving a narrow, elongated body portion with an upwardly curved bottomedge and a sharp lip protruding for a short distance from the forwardend of said body portion and a denture-anchoring post extending up fromthe forward end of the body portion, and which method also consists incutting a longitudinal slit in the mandible at a predetermined area inthe back of the mandible, making the width of said slit corresponding tothe width of the body portion of the implant, the depth of the slit notexceeding approximately 1 mm. the depth of said body portion, but thelength of said slip being less than three-fourths of the length of saidbody portion, inserting the section of said implant body portionopposite the post-carrying end into said slit, tapping said body portionfor the remainder of its length beyond said slit into the ramus and inbetween the lingual and buccal cortical plates of the ramus whilemaintaining the curved bottom edge of said body portion a desireddistance above the alvealor nerve, until said body portion is entirelyembedded in the mandible, and finally tapping said body portion in thereverse direction sufficiently to cause said sharp lip at the forwardend of said body portion to be thrust forwardly into the cortical mesialbone structure in front of said longitudinal slit, thereby preventingany possibility of the forward end of said body portion subsequentlybeing slightly lifted from its bed in the mandible.
 3. A dental implantdesigned specifically for insertion rearwardly into the ramus portion ofthe jawbone through an incision substantially along the longitudinalcenterline of the bone ahead of the ramus portion, said implant having asubstantially flat body portion with a width of approximately 2 mm., adepth not exceeding 6 mm. and an overall length of at least 30 mm., saidbody portion having an upwardly curved bottom edge, the top and bottomedges of said body poRtion converging at the rear end of said bodyportion to form a tip for facilitating the driving of the rear portionof said body portion rearwardly into the ramus, and an integral postextending up from the forward end of said body portion and adapted, whensaid body portion is implanted in the bone, to extend up through theepithelium to provide a denture anchorage, the angularity between saidpost and the top edge of said body portion being no greater than 90*. 4.The ramus implant of claim 3 with said body portion formed with aplurality of holes extending laterally therethrough, and with theaddition of a pointed lip extending from the front end of said bodyportion for a distance of approximately 3 mm., adapted to extendforwardly from the bone incision and under the cortical mesial bonestructure when the implant is tapped forwardly after insertion into theramus.